Additionally, any time a donation is made to a TeamRaiser participant, the donor's name and email address are automatically added as a contact in the participant center. As such, the participant can then send a thank you email to the donor and to solicit the donor for future events/gifts.

Another way contacts show up in the participant center is when the participant is a member of a team. If certain configurations are set (as outlined here), then the participant's teammates can be visible in the contacts.